雖然導致不平等的原因很多，但我們可以大體上把它們分為三類。一類是社會條件或家庭出身，例如在中國，與出生于貧困農村的人們相比，一個出生在大城市的人通常擁有更多的收入和更好的社會處境。另外一類是自然天賦，有些人天生聰明或健壯，有些人則天生愚笨或孱弱，前者一般也會比后者擁有更多的收入并處于更好的狀況。最后一類是抱負和努力程度，在其他條件相同的情況下，更有抱負和更努力的人們通常也會有更多的收入。

The causes of inequality are many ａｎｄ　varied, ａｎｄ　may be broadly grouped into three factors. The first is social condition ｏｒfamily background. In China, fｏｒexample, someone born ａｎｄ　bred in the city usually earns a higher income ａｎｄ　enjoys better social services. The second is aptitude. The cleverer ｏｒstronger ones usually earn more ａｎｄ　enjoy better conditions than the lesser endowed. The final one is ambition ａｎｄ　diligence. All things being equal, someone who aims higher ａｎｄ　works harder often earns more.